Question

One input terminal of the high gain comparator circuit is connected to ground and a sinusoidal voltage is applied to the other input. The output of comparator will be

A. A sinusoidal
B. A full rectified sinusoid
C. A half rectified sinusoid
D. A square wave

Answer 1

Hint: We know that a comparator is a device which compares two inputs two voltages or currents and outputs a digital signal either a \[1\] (the voltage at the plus side) or a \[0\] (the voltage at the negative side) indicating which is larger.

Complete answer:
The comparator circuit works simply by taking two analog input signals, comparing them and then producing the logical output high “\[1\]” or low “\[0\]”. When we apply an analog signal to the comparator’s positive input it is known as “non-inverting” and when we apply an analog signal to the comparator’s negative input it is known as “inverting input”.

If the analog input on non-inverting input is greater than the analog input on inverting then the output will swing to logical high output and when the analog input on non-inverting input is less than the analog input on inverting input, then the comparator output will swing to the logical low.

Here, the positive terminal of the comparator is grounded, which means that analog input voltage on the positive terminal of the comparator is $0$. When a positive cycle of input is applied to inverting terminal output is saturated to its negative maximum. That means the analog input on non-inverting input is less than the analog input on inverting input so the output will be logically low i.e. \[0\].

When a negative cycle is applied, output goes to the positive maximum value. That means that the analog input on non-inverting input is greater than the analog input on inverting so the output will be logical high i.e.\[1\]. So output is square wave.

Hence, the correct answer is option D.

Note: Application of comparator mainly involved in switching power regulators, BLDC operating motors and peak detectors. There are various types of comparators such as mechanical comparator, mechanical-optical comparator, reed type comparator, electrical-electronic comparator, pneumatic comparator.